Have you ever heard of a place called Eris? No, it’s not a city or even a country on Earth. It’s way, way out in our solar system, farther than the planet Neptune. Eris is a dwarf planet, discovered only in 2005 and named after a Greek goddess known for stirring up trouble. Eris is a fascinating place, and it holds a special record: it’s the biggest thing in our solar system that no spacecraft has ever visited.
Eris is big - really big - but how big exactly? Imagine you could line up about 2335 Earths side by side. That’s how long Eris is from one end to the other. To put it another way, Eris is about 1,445 miles in diameter. That’s more than the length of the entire United States from New York to Los Angeles! But we can’t just talk about how big Eris is without comparing it to some other objects in our solar system. After all, size is relative.
Just like our Earth has a moon, Eris has one too. Its moon is named Dysnomia, after the daughter of the goddess Eris in Greek mythology. Dysnomia orbits Eris; they travel together through the vastness of space.
When Eris was discovered, it seemed to be larger than Pluto. This led some people to call Eris the tenth planet in our solar system. But then, astronomers decided to define what a planet is for the first time. They decided that both Eris and Pluto are “dwarf planets,” not full-fledged planets. So, we went back to having eight planets in our solar system, just like before Pluto was discovered in 1930.
Eris may be far away and hard to visit, but that doesn’t make it any less interesting. This distant dwarf planet, with its own moon and a size comparable to that of Pluto, reminds us that there are still many wonders to discover in our vast solar system. Who knows what else we might find as we continue to explore the stars?
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